geostatistical analysis of pb, zn and cd concentration in soil of sepahanshahr suburb (south of esfahan)

generally heavy metals exist in all soils, but soil pollution is rising by time due to human activities. soils in the proximity of mines are more pruning to pollution of heavy metals due to mine exploring and excavation. this research was carried out to evaluate the soil pollution of sepahanshahr suburb with pb, zn and cd. during a field work campaign 100 soil samples were selected randomly from 9000 ha area. the soil samples were treated with 4 m hno3. total amounts of pb, zn and cd were measured using atomic absorption spectrometer. the results indicated that concentration of pb and zn were beyond the defined soil pollution thresholds (<50 ppm and 125-150 ppm for pb and zn, respectively) but of cd was below the threshold (1.5-2.5 ppm). therefore, physical development of the town towards the three studied mining sites, agricultural and mining activities should be seriously taken into account based up on environmental regulation and standards. analysis of variograms showed that structural component of spatial dependency dominates randomized component and the range spatial dependency was 3.3 km for all three elements. spatial distributions of pb, zn and cd were mapped using ordinary kriging. the kriging estimation variances for all three elements were calculated and delineated; the delineations indicated that variances were arised in the margins of the study area and in between the samples where, the density of sampling decreased.